This invention relates to an apparatus for measuring the sliver thickness in a drawing frame, particularly in a regulated drawing frame. The apparatus includes a sliver guiding device for guiding a plurality of simultaneously inputted fiber slivers at the inlet of the drawing frame. At least parts of the inner wall faces of the guiding device converge such that the side-by-side running slivers are brought together to form a sliver assembly in which the slivers assume a side-by-side contacting relationship in a single plane. Downstream of the guiding device, as viewed in the direction of sliver run, a roller pair is arranged which defines a nip through which the sliver assembly passes. By virtue of the frictional engagement in the nip, the roller pair pulls the sliver assembly through the sliver guiding device. Downstream of the roller pair the slivers diverge from one another. The sliver guiding device is associated with a biased, movable sensor element which, together with an operationally stationary counterelement, constitutes a constriction for the throughgoing sliver assembly. The sensor element executes excursions as the thickness of the sliver assembly changes. The displacements of the sensor element are applied to a transducer which, in response, generates control pulses. The counterelement situated opposite the sensor element may be adjusted and immobilized in its adjusted position.
In a known arrangement, in the absence of slivers in the sliver guiding assembly, the sensor element, urged by a biasing spring, moves into the outlet passage of the sliver guiding device and assumes a position close to, or even in contact with, the counterelement.